The invention relates to a system for monitoring the cover layer of a composite structure wherein the cover layer is subjected to wear. The element can, for example, be a cover layer of a conveyor belt and the system for monitoring this cover layer can include a transponder embedded in the body of the composite structure, a spatially fixed transmitter/receiver device mounted external to the composite structure with the transmitter/receiver device continuously generating an electromagnetic field; and, the transponder is supplied with energy in a receiving region of the transmitter/receiver device by the electromagnetic field and transmits data to the transmitter/receiver device when it is supplied with the energy.
The invention also relates to a method for monitoring a layer of a composite structure wherein the layer is subjected to wear. The method can be especially for monitoring the cover layer of a conveyor belt.
The monitoring of the cover layer of a conveyor belt is especially significant because too intense a wear of the cover layer of the conveyor belt can lead to damage of the latter and, in the extreme case, even to a tearing of the conveyor belt. This can have very expensive consequences and can cause delays in production. A reliable detection of the state of wear of the cover layer of a conveyor belt can contribute to a timely repair or replacement of the conveyor belt and to avoiding subsequent damage or production delays. Systems are already known from the state of the art which are directed to the reliable detection of the state of wear of the cover layer of a conveyor belt.
German patent publication 4,444,264 discloses a system for monitoring the cover layer of a conveyor belt of the kind referred to above. Each transponder, which is embedded in the conveyor belt coacts with a conductor loop. The conductor loops are embedded in the cover layer of the conveyor belt and the ends of the loops are directed upwardly in such a manner that the tips thereof are located at different distances from the surface of the cover layer. The transponder corresponding to a particular conductor loop is supplied with energy when the transponder is in the receiving region of the external spatially fixed transmitter/receiver device. The transponder transmits an individual identifier to the transmitter/receiver device. If there is wear of the cover layer of the conveyor belt, then the tip of the conductor loop is cut through depending upon the extent of the wear so that the transponder, which is assigned to this conductor loop, can no longer be supplied by the transmitter/receiver device with energy in the receiving region. In this case, the transmitter/receiver device receives no individual identifier from the transponder and this is an indication for the device that a specific wear is present at a specific location of the layer of the conveyor belt. The transmitter/receiver device can then initiate corresponding measures.
The system disclosed in German patent publication 4,444,264 is only suitable to a limited extent for monitoring the cover layer of a conveyor belt because the conductor loops, which are embedded in the cover layer, have a high mechanical sensitivity and therefore can be destroyed not only by wear of the cover layer but also for other reasons such as material fatigue.
German patent publication 195 25 326 likewise discloses a system for monitoring the cover layer of a conveyor belt of the kind referred to above. Several transponders are embedded in the cover layer of the conveyor belt at different spacings to the surface. The transponders transmit an individual identifier to an external transmitter/receiver device at a fixed location when the transponders come into the receiving region of this transmitter/receiver device. The transponders can become inoperative as a consequence of the wear of the cover layer of the conveyor belt in dependence upon the extent of the wear so that, for a continuing wear, ever fewer transponders transmit their individual identifier to the transmitter/receiver device. The transmitter/receiver device can determine the wear of the cover layer based on the non-transmittal of the individual identifier and, if needed, initiate appropriate measures.
The system disclosed in German patent publication 195 25 326 is suitable for monitoring the cover layer of a conveyor belt only to a limited extent because the transponders, which are embedded in the cover layer, can be prematurely destroyed not only because of the wear of the cover layer but also for other reasons such as the impact of individual pieces of goods to be conveyed. This case can especially occur when coarse material is conveyed and the transponder is located directly in the area of the belt which is subjected to the load. An indication of the wear is triggered in the transmitter/receiver device by a premature destruction of the transponder even though the cover layer of the conveyor belt is still present in its complete thickness.
It is an object of the invention to provide a system for monitoring a layer of a composite structure wherein the layer is subjected to wear. It is also an object of the invention to provide a system for monitoring the cover layer of a conveyor belt with which a reliable monitoring of wear of the layer subjected to wear is possible and wherein erroneous indications are avoided to the greatest extent possible. It is a further object of the invention to provide a method for monitoring a layer of a composite structure wherein the layer is subjected to wear. It is especially an object of the invention to provide a method for monitoring the cover layer of a conveyor belt wherein a reliable monitoring of wear is possible without erroneous indications.
The system of the invention is for monitoring a cover layer of a composite structure for wear with the cover layer having an outer surface and being subject to the wear during operation of the composite structure. The system includes: a transponder embedded in the composite structure; a transmitter/receiver device for continuously generating an electromagnetic field and the transmitter/receiver device being arranged spatially fixed outside of the composite structure; the transponder being disposed in a receiving region of the transmitter/receiver device so that the transponder can be supplied with energy by the electromagnetic field and can transmit data to the transmitter/receiver device when the transponder is supplied with energy; a ferromagnetic layer having a high permeability and being embedded in the cover layer between the transponder and the outer surface of the cover layer; and, the ferromagnetic layer being disposed to shield the transponder in the receiving region of the transmitter/receiver device so that the transmitter/receiver device receives no data from the transponder.
According to a feature of the method of the invention, a continuous check is made in the transmitter/receiver device as to whether data from a transponder are received with the transponder being embedded in the body of the composite structure. It is a feature of the method of the invention that measures are initiated by the transmitter/receiver device when data are received.
The basic idea of the invention is that the transponder is mounted in or at the body of the composite structure outside of the zone of wear of the cover layer. An announcement of the wear takes place when the ferromagnetic layer, which is assigned to the transponder, is destroyed over a large area by wear so that it loses its shielding effect.
The advantages achieved with the invention are especially that the wear of the cover layer can be reliably monitored without erroneous indications occurring because the ferromagnetic layer retains its shielding effect even when it is damaged slightly (for example, with a tear) and because the transponder is mounted below the ferromagnetic layer so that it is protected against the conventional mechanical loads of the body of the composite structure. For example, the impact load on the cover layer of the conveyor belt could be caused by a coarse object to be conveyed. A further advantage of the invention is that only the ferromagnetic layer of high permeability is destroyed with the wear of the cover layer because the transponder is mounted below this layer. This layer can be replaced easily and without great expense with a repair of the composite structure. The transponders, which are embedded in the body, are not destroyed with the wear of the cover layer.
According to another feature of the invention, the transmitter/receiver device is so mounted relative to the cover layer that the ferromagnetic layer of high permeability lies in the receiving region of the transmitter/receiver device between the transponder and the transmitter/receiver device.
According to another embodiment of the invention, the transmitter/receiver device is so mounted relative to the cover layer that the transponder lies in the receiving region of the transmitter/receiver device between the ferromagnetic layer and the transmitter/receiver device. In this embodiment, the transponder must be mounted directly next to the ferromagnetic layer of high permeability. It has been shown that, in this case, the transponder cannot be read out in the receiving region of the transmitter/receiver device even though it is located between the transmitter/receiver device and the ferromagnetic layer of high permeability.
According to another feature of the invention, the ferromagnetic layer of high permeability is substantially parallel to the surface of the layer subjected to wear. The advantage of this embodiment is that the entire ferromagnetic layer is located at a defined distance to the surface of the layer subjected to wear so that a defined wear is indicated when the ferromagnetic layer is destroyed over a large area by wear.
According to another feature of the invention, the ferromagnetic layer of high permeability is made of a metal foil. According to another embodiment, the ferromagnetic layer of high permeability comprises a wire lattice.
According to still another feature of the invention, the ferromagnetic layer of high permeability has a thickness of 0.1 mm to 2 mm. The advantage of this embodiment is that the ferromagnetic layer can also be embedded in an extremely thin wear layer and the wear of this layer can be reliably monitored. A further advantage of this embodiment is that a thin ferromagnetic layer of this kind is immediately destroyed when it is exposed by the wear of the layer subjected to wear. In this way, the critical wear is indicated directly.
According to another feature of the invention, the composite structure of the invention can include several layers and the transponder is mounted outside of the layer subjected to wear. The basic idea of this further embodiment is that the wear layer of the composite structure is subjected also to other mechanical loads to an especially great extent. Accordingly, the cover layer of the conveyor belt is, for example, subjected to conveyed goods so that it is there subjected to high mechanical loads. The transponder can be protected against these high mechanical loads either in that it is embedded as deep as possible in the cover layer or that it is embedded in another layer outside of the cover layer. The advantage of this embodiment of the invention is that the transponder embedded in the composite structure is protected especially well from the usual mechanical loads to which the composite structure is subjected.
According to still another embodiment of the invention, the transponder is operatively connected to a conductor loop, which is electrically conductive and is embedded in the composite structure below the ferromagnetic layer of high permeability. The advantage of this embodiment is that the transponder can be positioned at any desired location in the composite structure insofar as it can be supplied with energy via the conductor loop at this location. Preferably, the transponder is mounted at a location which is subjected to an especially low mechanical load of the unit in daily use. Preferably, the conductor loop is mounted outside of the layer subjected to wear for a composite structure comprising several layers. In this case, the conductor loop is protected especially well against the mechanical loads which operate on the composite structure during normal use.
According to still another embodiment of the invention, several ferromagnetic layers of high permeability are embedded in a cover layer subjected to wear. These ferromagnetic layers are located at different layer depths and each layer is assigned to at least one transponder. The advantage of this embodiment is that different degrees of wear of the layer subjected to wear of the composite structure can be monitored. The transmitter/receiver device can first output a warning for a slight wear; however, the device can prevent a further use of the composite structure when there is advanced wear.
According to another embodiment of the invention, each of the transponders embedded in the composite structure transmits an individual identifier to the transmitter/receiver device when it is supplied with energy by the device. The advantage of this embodiment is that the position of the transponder is detected based on the individual identifier from the transmitter/receiver device and, therefore, the position of the wear is detected when the device receives the individual identifier of the transponder.